The proposed research is designed to replicate and extend previous observations indicating that immune processes are subject to regulation by the central nervous system. Specifically, we are concerned with the effects of conditioning. Using an illness-induced taste aversion paradigm, rats and/or mice are conditioned by pairing a distinctively flavored drinking solution, e.g., saccharin (the conditioned stimulus) with cyclophosphamide or other immunosuppressive (or potentiating) drug (the unconditioned stimulus). After conditioning, animals are injected with antigen (e.g., sheep erythrocytes, trinitrophenol-lipopolysaccharide). Antibody titers are measured after immunogenic stimulation in conditioned animals that are again exposed to the conditioned stimulus or that receive no further experimental treatment, and in nonconditioned and placebo-treated groups. The effects of conditioning on cell mediated immune responses and on experimentally induced (experimental allergic encephalomyelitis) and naturally occurring (autoimmune disease in NZBxNZW F1 mice) disease processes are also being examined. The primary focus of this initial research is to study systematically those parameters of the conditioning process and those parameters of the immune response which are optimal for inducing conditioned immunobiologic responses and for an analysis of the mechanisms mediating such immunobiologic responses.